﻿<p><em>IfcRevolvedAreaSolidTapered</em> is defined by revolving a
cross section along a circular arc. The cross section may change
along the revolving sweep from the shape of the start cross
section into the shape of the end cross section. Corresponding
vertices of the start and end cross sections are then connected.
The bounded surface may have holes which will sweep into holes in
the solid.</p>
<p>The rotation axis is defined by:</p>
<ul>
<li>Start point:
<em>SELF\IfcSweptAreaSolid.Position.Location</em></li>
<li>Direction: <em>SELF\IfcRevolvedAreaSolid.Axis</em></li>
<li>Rotation axis: <em>SELF\IfcRevolvedAreaSolid.AxisLine</em>,
created from start point and direction by appying a 1 unit
magnitude.</li>
<li>Orientation: Positive angles are applied clockwise when
looking into the positive direction of the rotation axis.</li>
</ul>
<p>The start cross section is defined by
<em>SELF\IfcSweptAreaSolid.SweptArea</em>:</p>
<ul>
<li>A bounded planar surface lying in the XY plane of the
position coordinate system defined by
<em>SELF\IfcSweptAreaSolid.Position.P[1]</em> and
<em>SELF\IfcSweptAreaSolid.Position.P[2]</em></li>
<li>The rotation axis lies in the plane of the start cross
section but shall not intersect the interior of the start cross
section.</li>
</ul>
<p>The end cross section is defined by <em>EndSweptArea</em>:</p>
<ul>
<li>A bounded planar surface lying in the XY plane of the
position coordinate system defined by rotating the start position
coordinates provided by <em>SELF\IfcSweptAreaSolid.Position</em>
around the rotation axis by the angle given by
<em>SELF\IfcRevolvedAreaSolid.Angle</em>.</li>
<li style="list-style: none">
<ul>
<li>The end cross section is topologically similar to the start
cross section (having the same number of vertices and edges).</li>
<li>The end cross section can either be defined by the same
paramteric profile using different parameter values, or by a 2D
Cartesian transformation of the start profile within the end
cross section plane.</li>
</ul>
</li>
</ul>
<p>The solid is generated by transforming the start cross section
into to end cross section. A start face, an end face (each
defined by start and end cross sections), and one or more lateral
faces. Each lateral face is a ruled surface defined by a pair of
corresponding edges of the start and end section. The ruled
surfaces are constructed in the cylindrical coordinate space
defined by the supertype <em>IfcRevolvedAreaSolid</em>.</p>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC4.
</blockquote>

<p class="spec-head">Informal Propositions:</p>
<ol>
<li>Mirroring within <em>IfcDerivedProfileDef.Operator</em> shall
not be used</li>
</ol>